The present invention relates to water filters. Typically, such filters comprise a hollow core cylindrical block of bonded, activated charcoal. Water flows through the perimeter of the charcoal filter and into the center core from whence it flows to the user. Typically, some type of porous plastic sleeve is located in the core to keep the charcoal from flaking off into the water.
One problem with such filters is that if the charcoal particles are fine enough to do a proper filtering job, they inhibit water flow substantially. One prior artisan has attempted to overcome this by cutting longitudinal grooves in the outer peripheral surface of the filter. However, it is believed that this merely causes water to flow through the filter at the base of the groove and effectively or substantially eliminates water flowing through an outer layer of the filter.
Another problem with bonded charcoal particle filters is that the plastic binder used to bond the charcoal particles together tends to clog the pores of the activated charcoal. While such clogging does not completely eliminate the effectiveness of the activated charcoal, it does tend to reduce its efficiency.
U.S. Pat. No. 3,950,251 discloses a cylindrical filter element formed of a polymer bonded, compressed charcoal inner core with a porosity of about 10 microns and a second outer filter element sleeve made up of unbonded granular activated charcoal of 14 to 40 mesh particle size. A serious problem with such an arrangement is that the outer sleeve of unbonded charcoal has to be contained in a porous plastic container to keep the charcoal from spilling out of the filter during shipping and storage.
Also, water tends to "channel" through the unbonded outer charcoal without being filtered. On the other hand, bonding can substantially limit the effective surface area of the larger particles, in that the binder clogs the pores. The effective surface area of the larger particles is already less per unit of weight than that of the smaller inner particles, and the binder aggravates the problem.